Optometric apparatus

ABSTRACT

An optometric apparatus comprises: a pair of right and left lens chamber units, each unit including a test window and optical elements to be selectively disposed in the test window; and a controller including a transmitting part which transmits a control signal in the form of an optical signal to the lens chamber units to selectively dispose the optical elements in the test window, the transmitting part being adapted to widen an extent of diffusion of luminous flux of the optical signal more greatly in a forward to upward directions than in a lateral direction.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optometric apparatus forsubjectively examining (measuring) a refractive power of an eye of anexaminee.

[0003] 2. Description of Related Art

[0004] There has been known an optometric apparatus constructed tosubjectively examine (measure) a refractive power (a visual acuity) ofan eye of an examinee by presenting optotypes forward of the eye throughan optical element such as a spherical lens and cylindrical lens placedin front of the eye. In this optometric apparatus, a plurality of lensdisks, each holding various optical elements are rotatably placed ineach housing of a right and left lens chamber units each having a testwindow. Each lens disk is rotated by a motor to selectively dispose theoptical elements into the test window. Some optometric apparatuses ofthis type include a wireless controller which transmits a control signalin the form of an optical signal to the motor and others associated withthe lens chamber units.

SUMMARY OF THE INVENTION

[0005] The present invention has been made in view of the abovecircumstances and has an object to overcome the above problems and toprovide an optometric apparatus provided with a wireless controller withhigh operationality.

[0006] Additional objects and advantages of the invention will be setforth in part in the description which follows and in part will beobvious from the description, or may be learned by practice of theinvention. The objects and advantages of the invention may be realizedand attained by means of the instrumentalities and combinationsparticularly pointed out in the appended claims.

[0007] To achieve the purpose of the invention, there is provided anoptometric apparatus comprising: a pair of right and left lens chamberunits, each unit including a test window and optical elements to beselectively disposed in the test window; and a controller including atransmitting part which transmits a control signal in the form of anoptical signal to the lens chamber units to selectively dispose theoptical elements in the test window, the transmitting part being adaptedto widen an extent of diffusion of luminous flux of the optical signalmore greatly in a forward to upward directions than in a lateraldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings, which are incorporated in andconstitute a part of this specification illustrate an embodiment of theinvention and, together with the description, serve to explain theobjects, advantages and principles of the invention.

[0009] In the drawings,

[0010]FIG. 1 is a schematic structural view of an optometric systemincluding an optometric apparatus in a preferred embodiment;

[0011]FIG. 2 is a schematic structural view of the optometric apparatus;

[0012]FIG. 3 is a schematic structural view of the optometric apparatus;

[0013]FIG. 4 is a schematic structural view of a disk cover;

[0014]FIG. 5 is a schematic structural view of a moving mechanism of theoptometric apparatus;

[0015]FIG. 6 is a schematic structural view of a controller;

[0016]FIG. 7A shows a diffusion part in front, right side, and bottomviews;

[0017]FIG. 7B is a sectional side view of the diffusion part;

[0018]FIG. 7C is a schematic side view of a signal transmitting part;

[0019]FIG. 8 is a schematic block view of a control system in theoptometric system in the embodiment;

[0020]FIG. 9 is a view explaining a principle for determining aconvergence angle and a PD correcting distance; and

[0021]FIG. 10 is a view showing a diffused state of a control signal bya diffusing part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] A detailed description of a preferred embodiment of the presentinvention will now be given referring to the accompanying drawings. FIG.1 is a schematic structural view of an optometric system including anoptometric apparatus in the present embodiment. FIGS. 2 and 3 areschematic structural views of the optometric apparatus seen from anoperator side.

[0023] A main unit 1 of the optometric apparatus includes a pair ofright and left lens chamber units 60 having symmetric shapes, eachhaving a test window 61, and a movement unit 6 supporting (holding) thelens chamber units 60 in a hanging state. The movement unit 6 houses amovement mechanism 40 (see FIG. 5) including a slide mechanism foradjusting the interval between the right and left lens chamber units 60and a convergence mechanism for adjusting a convergence angle (an inwarddirecting angle) of the lens chamber units 60.

[0024] The main unit 1 is supported above a table 10 by a support arm 4provided on the table 10. By operation of a switch 11 for verticalmovement, unillustrated driving means is driven to vertically move thetable 10 to adjust the height of the top plate of the table 10, namely,the height of the main unit 1.

[0025] An optotype presenting device 20 to be used for a far visionexamination is placed at a predetermined distance (e.g., 1 m) from themain unit 1 (FIG. 1 schematically shows the inner structure of thisdevice 20). The device 20 internally includes an optotype presentingpart 21 for presenting various examination optotypes, a beam splitter22, a concave mirror 23, and others. The light of the optotype from thepresenting part 21 passes through the beam splitter 22 and is reflectedby the mirror 23. The optotype light reflected by the mirror 23 isreflected by the beam splitter 22 toward an examinee's eye E through awindow 24.

[0026] A rod 2 is connected to an attachment member 8 provided in themovement unit 6. On the rod 2, an optotype presenting unit 3 for use ina near vision examination is mounted movably (slidably) in the axial(longitudinal) direction of the rod 2. This unit 3 includes a chart 3 afor the near vision examination on which a plurality of examinationoptotypes are drawn or printed. The near vision chart 3 a is rotatableabout an axis 3 b of the presenting unit 3. By rotation of this chart 3a, a desired one of the optotypes is presented in a presenting window 3c. The presenting unit 3 is hung on the rod 2 so that the height of thechart 3 a to be presented in the presenting window 3 c is the same asthe height of the test window 61. The rod 2 is graduated to show adistance (a distance for the near vision examination distance,hereafter, a near-vision distance) from the eye E positioned in front ofthe test window 61 to the chart 3 a. Thus, in the near visionexamination, the chart 3 a can be disposed in advance at a desireddistance from the eye E. The attachment member 8 is constructed to flipup the rod 2 connected thereto. Accordingly, the rod 2 can be held in aflipped-up position as shown in FIG. 1 except during the near visionexamination.

[0027] A controller 30 includes switches for operating the main unit 1and the optotype presenting device 20 and switches for automatically ormanually performing the far vision examination and the near visionexamination. The controller 30 will be mentioned in detail later.

[0028] A signal receiving part 5 is provided in the main unit 1 toreceive a control signal from the controller 30. This receiving part 5includes a light receiving element (photoreceptor) sensitive to infraredlight. A liquid crystal display (LCD) 7 is used to display informationon the control signal from the controller 30 (for example, data onspherical power, cylinder power, and others of an optical element 65 tobe disposed in the test window 61 and data on an optotype to bepresented). A relay unit 9 is built in the table 10 and linked to theoptotype presenting device 20 and others. This relay unit 9 is used totransmit the control signal which the main unit 1 receives from thecontroller 30, to the optotype presenting device 20 and others asrequired.

[0029] In a housing of each lens chamber unit 6, a plurality of lensdisks 64 are rotatably placed, on each of which many various opticalelements (lenses and the like) 65 are mounted (held) in acircumferential arrangement. Each lens disk 64 is rotated by operationof the controller 30 to selectively dispose one of the optical elements65 into the test window 61. As shown in FIG. 3, the housing of each lenschamber unit 60 includes a main cover 62 a and a disk cover 62 b. Whenthe disk cover 62 b is detached from the main cover 62 a, a part (abouthall) of the circumferential edge of each lens disk 64 placed in thehousing is exposed. At this time, only the part of each lens disk 64 isexposed from the main cover 62 a, and other mechanisms and electricsystems remain covered, not exposed.

[0030] As shown in FIG. 4, the disk cover 62 b is of a semicircularshape in front view (see FIG. 3) and has an inner cavity. This diskcover 62 b is provided with the test windows 61 in semicircular frontand rear faces which will face an examinee and an examiner respectively.The disk cover 62 b is further provided, at upper and lower ends, withattaching members 66 each having a hole 66 a which a screw 63 serving asattachment means passes through. Correspondingly, the main cover 62 a isprovided with female screw portions not shown for attachment of the diskcover 62 b. To attach the disk cover 62 b to the main cover 62 a, thescrews 63 passing through the holes 66 a of the attaching members 66 aretightened into the female screw portions. To detach the disk cover 62 bfrom the main cover 62 a, on the other hand, the screws 63 are simplyloosen and taken off from the female screw portions. In this manner, thedisk cover 62 b can easily be attached and detached.

[0031] When the disk cover 62 b is detached, the inside of each testwindow 61 can easily be cleaned. It is also possible to easily clean theoptical elements 65 mounted in each lens disk 64. Because each lens disk64 can be rotated manually by a person (for example, an examiner) whoholds the exposed portion thereof, all of the optical elements 65 areallowed to be cleaned. Each lens disk 64 has an opening with no lens.

[0032] In the present embodiment, the disk cover 62 b provided with thetest windows 61 is adapted to be detachably attached. Instead thereof, astructure that only the test windows 61 are detachably attached may beadopted. This structure that only the test windows 61 are detachablyattached is realized, for example, in such a manner that a holder whichholds transparent members such as glass and plastic resin forming thetest windows 61 is screwed or mounted by click mechanism in the housingof each lens chamber unit 60. With this structure, the test windows 61can be attached and detached together with the holder. In this case, adial switch 31 b (see FIG. 6) on the controller 30 is operated to bringthe optical elements 65 mounted in each lens disk 64, one by one, to aposition where the test window 61 has been detached so that all of theoptical elements 65 can be cleaned in turn.

[0033] In many cases, dirt on the inside of each test window 61 iscaused when moisture including dust and oil content evaporated due toincreased temperature of the inside of the main unit 1 by heating of amotor adheres to and condenses on the test window 61 exposed to outsideair, resulting in residual dew condenses or dried marks thereof. Toprevent the generation of the dew condenses, the test window ispreferably structured as a double-layer test window which serves as aheat insulating layer or a test window provided with heating wire.

[0034] The movement mechanism 40 is explained below with reference toFIG. 5. Shafts 42 fixed to hanging plates 41 which hang the lens chamberunits 60 respectively are rotatably engaged in holes 43 a of slidablebases 43. Shafts 44 for slanting the hanging plates 41 in an inwarddirection are connected to worms 46 a and 46 b respectively throughgears 46. At one end (lower end in FIG. 5) of each of the shafts 44, aneccentric shaft 51 is attached. The tip end portion of the eccentricshaft 51 is engaged in a groove 41 a formed in the hanging plate 41 a.The worms 46 a and 46 b are connected to driving means including a pulsemotor 47, and will be rotated by rotation of the motor 47. The rotationof the worms 46 a and 46 b causes the eccentric shafts 51 to rotate byway of the gears 45 and the shafts 44, thereby converging the hangingplates 41. The slidable bases 43 are movable (slidable) on a fixed guide48 in its axial direction. Driving means including a pulse motor 49 andthe fixed guide 48 are secured to a fixed bracket not shown. Screws 50 aand 50 b having threading directions opposite to each other areconnected to the motor 49 and are engaged with female screws of theslidable bases 43. When the motor 49 is rotated, accordingly, the twoslidable bases 43 are moved (slid) in opposite directions. By means ofthe movement mechanism 40 having the above structure, an interval and aconvergence angle between the right and left lens chamber units 60 (theright and left test windows 61) are adjusted.

[0035] Referring to FIG. 6, the controller 30 is explained below. Thiscontroller 30 is of a shape and size allowing an examiner to handle byone hand. The controller 30 includes a switch part 31 for variousoperations. This switch part 31 includes an optotype switch group 31 afor selecting a desired optotype from a plurality of optotype groups,the dial switch 31 b for selecting various functions, inputtingnumerals, and disposing the optical element 65 satisfying examinationconditions (spherical power, cylinder power, axis, etc.) into the testwindow 61, an input switch 31 c for inputting data on objectivemeasurement results, a start switch 31 d for starting a programmedeye-examination (optometry), a program advance switch 31 e, a PD switch31 d for setting (inputting) a pupillary distance (PD), and a menuswitch 31 g for setting various examination conditions. In the presentoptometric apparatus, the PD can be set in 1 mm steps in a range of 48mm to 80 mm.

[0036] In the top of the controller 30, there is provided a signaltransmitting part 32 including a light emission part 32 a including anLED which emits infrared light to be used for a control signal and adiffusion part 32 b attached just ahead of the light emission part 32 a.The diffusion part 32 b serves to widely diffuse the control signalemitted from the light emission part 32 a so that the outgoing directionof the signal is greatly extended from forward to upward.

[0037]FIG. 7 are schematic structural views of the transmitting part 32;specifically, FIG. 7A shows the diffusion part 32 b in front, rightside, and bottom views; FIG. 7B is a sectional side view of thediffusion part 32 b; and FIG. 7C is a schematic side view of thetransmitting part 32.

[0038] The diffusion part 32 b is an optical member of a substantiallycylindrical shape, made of a transparent resin such as acrylate resin.This diffusion part 32 b has an end cut out in half circular face at aslant, forming a beveled face 33. This beveled face 33 is formed at aslant angle determined so that an incident angle θ₁ of luminous flux(optical signal) from a horizontal direction onto the beveled face 33 isa critical angle or more in order to totally reflect the luminous flux.Furthermore, the beveled face 33 is also configured to have the slantangle of 45° or less with respect to the center axis (in a longitudinaldirection) of the diffusion part 32 b so that the luminous flux isturned upward and then goes forward.

[0039] The diffusion part 32 b in the present embodiment is made ofacrylate resin with a reflective index of 1.49. When the luminous fluxpasses from this acrylate resin into air, an incident angle θ₁ of theluminous flux becomes the critical angle at approx. 42.15°. Accordingly,to provide an incident angle θ₁ larger than the critical angle and allowthe luminous flux turned (reflected) upward to go forward, the slantangle of the beveled face 33 is set at 35° (the incident angle θ₁, 55°).

[0040] In the present embodiment, the incident angle θ₁ to the beveledface 33 is set to be larger than the critical angle in order to totallyreflect the luminous flux from the horizontal direction, but it is notlimited thereto.

[0041] For instance, the beveled face 33 may be applied with a coatinghaving a property of totally reflecting infrared light or partiallyreflecting infrared light at a predetermined ratio.

[0042] The controller 30 is formed at its top with a recess not shown inwhich the diffusion part 32 b is mounted, and the light emission part 32a is centrally placed in the recess. As shown in FIG. 7B, the diffusionpart 32 b is formed at its bottom with a recess 34 having apredetermined depth in the axial direction of the diffusion part 32 b.This recess 34 serves to internally hold the light emission part 32 awhen the diffusion part 32 b is mounted in the recess of the controller30. With this structure, the diffusion part 32 b is easily detachablymounted in the controller 30.

[0043] The diffusion part 32 b is mounted in the controller 30 so thatthe beveled face 33 is oriented downward. When infrared light for thecontrol signal is emitted from the light emission part 32 a of thecontroller 30 in which the diffusion part 32 b has been mounted, anupper portion of the emitted luminous flux travels in straight linesthrough and then directly exits the diffusion part 32 b in a forwarddirection. A lower portion of the emitted luminous flux similarlytravels in straight lines through the diffusion part 32 b and thentotally or partially reflected at the beveled face 33 to go upward.

[0044]FIG. 10 are views showing a diffused state of the infraredluminous flux for the control signal from the transmitting part 32. Asshown in FIG. 10A, the extent of diffusion of the luminous flux inforward to upward directions is greater than that in the case where thediffusion part 32 is not mounted in the controller 30. As shown in FIG.10B, on the other hand, the extent of diffusion of the luminous flux ina lateral direction is substantially the same as in the case where thediffusion part 32 is not mounted in the controller 30.

[0045] As above, the luminous flux is not diffused in all directions butis diffused only vertically from the forward direction to the upwarddirection. This makes it possible to allow the receiving part 5 providedin the main unit 1 positioned above the controller 30 to receive thecontrol signal from the controller 30 disposed on the table 10 as shownin FIG. 2 while keeping a reduction in light intensity to the minimum.Consequently, there is no need for the examiner to operate thecontroller 30 while pointing it at the receiving part 5. Accordingly,operationality and convenience of the controller 30 can be enhanced.When the orientation of the diffusion part 32, which is rotatablymounted, is changed, the traveling direction of the infrared light for acontrol signal can be changed correspondingly.

[0046] The emission part 34 may include a plurality of LEDs havingdifferent placement angles. Further, just ahead of the emission part 34,there may be placed an optical member capable of deflecting luminousflux, such as a cylindrical lens. In this case, the luminous flux can bediffused more widely from the frontward direction to the upwarddirection.

[0047] The operation of the optometric system having the above structureis described below with reference to a schematic block view of a controlsystem shown in FIG. 8. Herein, a subjective examination (far vision andnear vision examinations) is performed by use of an examination programdetermined in advance in relation to procedures of the subjectiveexamination including the near vision examination.

[0048] It is to be noted that the optometric apparatus used in thepresent embodiment has a structure that, if the examinee's PD is 54 mmor less in the near vision examination using the near-vision distance of35 cm from the eye E to the near vision chart 3 a, the right and leftlens chamber units 60 when correspondingly moved closer and convergedwill come into contact with each other.

[0049] After having the examinee to sit down in front of the main unit1, the examiner operates the switch 11 to adjust the height of the testwindow 61 to the height of the eye E. The examiner then operates theinput switch 31 c on the controller 30 for input (transfer) of objectiveexamination data (spherical power, cylinder power, axis, pupillarlydistance, etc.) into the main unit 1. On pressure of the input switch 31c, the microcomputer 35 in the controller 30 transmits a control signalfrom the transmitting part 32 for transfer of the objective examinationdata from an objective refractive power measurement device 100 to themain unit 1. The receiving part 5 in the main unit 1 receives thecontrol signal transmitted from the transmitting part 32. In response tothe control signal received by the receiving part 5, a microcomputer 70in the main unit 1 obtains the objective examination data from theobjective refractive power measurement device 100 by way of the relayunit 9 and stores the data in a memory 71.

[0050] Based on the PD data inputted, the microcomputer 70 drives themovement mechanism 40 to move (slide) the right and left lens chamberunits 60 to adjust the interval between the lens chamber units 60 to theexaminee's PD. Based on the other objective examination data, themicrocomputer 70 also drives the pulse motor 74 to rotate each lens disk64, thereby disposing appropriate ones of the optical elements 66 havinga predetermined power (diopter) in the test window 61. Simultaneously,the test window 61 not to be used is shielded.

[0051] Then, the examiner pushes the start switch 31 d on the controller30 to start the examination program. Upon pressure of the switch 31 d,the microcomputer 35 transmits the control signal from the transmittingpart 32 to present an optotype corresponding to the examination steps ofthe examination program the optotype presenting device 20. Themicrocomputer 25 in the optotype presenting device 20 receives thecontrol signal from the receiving part 5 via the relay unit 9 and, inaccordance with this control signal, drives the optotype presenting part21 to project an optotype light toward the eye E.

[0052] The examiner operates the program advance switch 31 e to advancethe examination program to sequentially perform a spherical poweradjustment, an axis measurement, a cylinder power measurement, andothers, thereby determining a correction power for far vision to each ofthe left and right eyes. When further advanced, the program goes into anear vision examination step. At this time, an examination mode of theapparatus is switched from a far vision examination mode to a nearvision examination mode.

[0053] To execute the near vision examination, the examiner turns therod 2 down from the flipped-up position to a horizontal position toplace the optotype presenting unit 3 in front of the test window 61,i.e., the eye E as shown in FIG. 2. The examiner moves (slides) the unit3 on the rod 2 in its axial direction to provide a near-vision distance(a presenting distance) necessary for the examinee. This near-visiondistance has been determined in advance (36 cm in the presentembodiment). To change the near-vision distance to 50 cm, 70 cm, orothers, the examiner operates the menu switch 31 g on the controller 30to establish a near-vision distance changing mode and selects anappropriate near-vision distance with the dial switch 31 b. To changethe PD information, the examiner should operates the PD switch 31 f toestablish a PD changing mode and changes (sets) the PD information withthe dial switch 31 b. A screen for the above changes is displayed in thedisplay 7 of the main unit 1. The near-vision distance in the optometricapparatus in the present embodiment can be selected in 5 cm steps in arange of 35 cm to 70 cm.

[0054] When receives the signal representing the switching to the nearvision examination mode or thereafter the near-vision distance isselected with the controller 30, the microcomputer 70 drivingly controlsthe movement mechanism 40 based on the received near-vision distanceinformation and PD information to converge and move (slide) the rightand left lens chamber units 60. This driving-control of the movementmechanism 40 is performed by control of driving amounts (the number ofpulses) of the pulse motors 47 and 49.

[0055] Specifically, the right and left lens chamber units 60 areconverged and moved (slid) by changing a convergence angle to beappropriate for the PD of the examinee and the presenting distance(near-vision distance) of the near vision chart 8 a and by moving thelens chamber units 60 closer to each other by a predetermined distanceto narrow the interval between the right and left test windows 61(hereinafter, referred to as “PD correction”). This PD correction isperformed because the PD in the near vision examination becomes narrowerthan that in the far vision examination due to the convergence of theexaminee's eyes.

[0056]FIG. 9 is an explanatory view to show the principle fordetermining the convergence angle and the PD correcting distanceaccording to the examinee's PD and the presenting distance (near-visiondistance) of the near vision chart 3 a. In FIG. 9, numeral 104 is acycloduction point; 101, a corneal vertex point (in far vision); 102, acenter of rotation of each shaft 42; and 103, a near-vision fixing pointwhere the near vision chart 3 a is placed. Assuming that each distancebetween the cycloduction point 104 and the near-vision fixing point 103is 8, b, and c, and the PD in far vision is d, a convergence angle θ₂ ofthe lens chamber units 60 is expressed by the following expression (1):$\begin{matrix}{\theta_{2} = {\tan^{- 1}\frac{d}{2\left( {a + b + c} \right)}}} & (1)\end{matrix}$

[0057] Further, the PD correcting distance, e, in this stage isexpressed by the following expression (2):

e=(a+b)tan θ₂  (2)

[0058] Using the above expressions, the convergence angle and the PDcorrecting distance can be determined.

[0059] Based on the examinee's PD and the presenting distance(near-vision distance) of the near vision chart 3 a, as above, theconvergence and PD correction of the right and left lens chamber units60 are performed to substantially align the visual axis of the eye Ewith the optical axis of the optical element 65 disposed in the testwindow 61 during the near vision examination.

[0060] In the case where the examinee's PD is narrow, however, the lenschamber units 60 are likely to contact with each other when theconvergence and PD correction of the lens chamber units 60 are made sothat the visual axis of the eye E matches the optical axis of theoptical element 65 (hereinafter, referred to as “full convergence”). Inthe present embodiment, therefore, the optometric apparatus is adaptedto perform the convergence and the PD correction in different mannersbetween the case where the units 60 are likely to contact with eachother and the other case where the units 60 are unlikely to contact witheach other.

[0061] Table 1 shows the convergence and the PD correction of the lenschamber units 60 for each PD in the optometric apparatus with thenear-vision distance of 35 cm. In Table 1, a “convergence angle (Full)”is a convergence angle needed to achieve full convergence and a“convergence angle (Actual)” is a convergence angle in the presentembodiment. A “PD correcting distance (Full)” and a “PD correctingdistance (Actual)” are also used similarly to the above “convergenceangle (Full)” and others. A “PD correcting distance (Limit)” indicates aPD correcting distance limit to which the PD correction is allowed. Theconvergence angle and the PD correcting distance are calculated byrounding off the number to the first decimal place for convenience TABLE1 Presence/absence PD of contact due (in far CA CA PD CD PD CD PD CD tofull converging vision) (Full) (Actual) (Full) (Actual) (Limit) motion56 mm 4.4° 4.4° 5.6 mm 5.6 mm — Absence 54 mm 4.3° 4.3° 5.4 mm 5.4 mm —Absence 52 mm 4.1° 2.8° 5.2 mm 3.6 mm 4.4 mm Presence 50 mm 3.9° 1.4°5.0 mm 1.8 mm 2.6 mm Presence 48 mm 3.8° 0° 4.8 mm   0 mm   0 mmPresence

[0062] As seen in Table 1, in the case where the near-vision distancewas 35 cm and the examinee's PD (in the far vision examination) was 54mm or more (54 mm to 80 mm), the lens chamber units 60 did not contacteven when the full convergence was performed. To make the fullconvergence for the PD of 54 mm, for example, the convergence angle ofthe lens chamber units 60 needs be set at 4.3° and the PD correctingdistance, at 5.4 mm. Because the contact will not be caused when the PDis 54 mm, for actual convergence of the lens chamber units 60, theconvergence angle can be set at 4.3° and the PD correcting distance, at5.4 mm.

[0063] In the case where the full convergence can be performed based onthe near-vision distance and the examinee's PD set as above withoutcausing the contact between the lens chamber units 60, these units 60are converged and moved for the PD correction so that the visual axis ofthe eye E substantially matches the optical axis of the optical element65.

[0064] On the other hand, in the case where the examinee's PD (in thefar vision examination) is 54 mm or less, as shown in Table 1, the fullconvergence to substantially align the visual axis of the eye E with theoptical axis of the optical element 65 results in the contact betweenthe lens chamber units 60. In this case, the microcomputer 70 determinesthe convergence angle and the PD correcting distance in a range thatwill not cause the contact between the lens chamber units 60, eventhough the optical axis of the optical element 65 is not substantiallyaligned with the visual axis of the eye E, and then drives the movementmechanism 40 based on the determined settings. This makes it possible toreduce the prismatic effect caused by the optical element 65 to theminimum.

[0065] In the present embodiment, when the PD is 54 mm, the fullconvergence of the lens chamber units 60 can be achieved with theconvergence angle of 4.3° and the PD correcting distance of 5.4 mm. Whenthe PD is 48 mm, the driving of the lens chamber units 60 is disabled.Thus, the convergence angles and the PD correcting distances for targetPDs (48 mm to 54 mm in the present embodiment), for which the driving ofthe lens chamber units 60 is enabled, are equally divided in that rangeand the convergence angle and the PD correcting distance for actuallyconverging the lens chamber units 60 and moving them for the PDcorrection are determined.

[0066] For instance, to perform the full convergence for the examinee'sPD of 52 mm, it is necessary to set the convergence angle of the lenschamber units 60 at 4.1° and the PD correcting distance at 5.2 mm asshown in Table 1. However, based on the convergence angle of 2.8° andthe PD correcting distance of 3.6 mm, the lens chamber units 60 areactually converged and moved for the PD correction. For the examinee'sPD of 50 mm, the convergence and the PD correction of the lens chamberunits 60 are actually performed based on the convergence angle of 1.4°and the PD correcting distance of 1.8 mm. Those conditions have beenstored in advance in the memory 71 so that the microcomputer 70selectively determines an appropriate of the conditions from the memory71 according to the inputted pupillary distance and near-visiondistance.

[0067] In the present embodiment, the case where the near-visiondistance is 35 cm is explained. In the other cases where the near-visiondistance is not 35 cm, the same control of convergence and PD correctionis similarly executed when the contact between the lens chamber units 60is likely caused due to the examinee's PD.

[0068] In the present embodiment, the convergence angles and the PDcorrecting distances for the PDs of 48 mm to 54 mm are equally dividedin that range and the convergence angle and PD correcting distance foractually converging the lens chamber units 60 and moving them for the PDcorrection are used, but they are not limited thereto. As shown in the“PD correcting distance (Limit)” in Table 1, for the PDs which arelikely to cause the contact between the lens chamber units 60, theconvergence angle limit and the PD correcting distance limit for each PDmay be set and the convergence and the PD correction of the lens chamberunits 60 may be performed based on those set values. In the case wherethe near-vision distance is 35 cm and the examinee's PD is 52 mm, forexample, the convergence angle is set at 2.8° and the PD correctingdistance is set at 4.4 mm which is a limit for this convergence angleand the convergence and PD correction of the lens chamber units 60 areperformed.

[0069] The prismatic effect caused due to misalignment between thevisual axis of the eye E and the optical axis of the optical element 65can be reduced more largely by adjustment of the PD correcting distancerather than by adjustment of the convergence angle. Thus, the PDcorrecting distance may be determined at a limit or in preference to theconvergence angle and adjusted.

[0070] After completion of the convergence and the PD correction of thelens chamber units 60, the examiner carries out the near visionexamination on the examinee's right and left eyes respectively to checka spherical power and others. Under the above control, the convergenceand the PD correction of the lens chamber units 60 are performed to acertain extent even in the case where the units 60 are likely tocontact. Accordingly, the optometric apparatus according to theinvention enables high-precision examination as compared with theconventional apparatus. After the near vision examination, upon pressureof a switch not shown on the controller 30, the examination data can beprinted out. Based on a signal from this print switch, the examinationprogram is terminated.

[0071] In the above embodiment, the explanation is made by using theexamination program of carrying out the far vision examination and thenear vision examination in sequence. Alternatively, the presentinvention can be applied to another case where only the near visionexamination is performed.

[0072] While the presently preferred embodiment of the present inventionhas been shown and described, it is to be understood that thisdisclosure is for the purpose of illustration and that various changesand modifications may be made without departing from the scope of theinvention as set forth in the appended claims.

What is claimed is:
 1. An optometric apparatus comprising: a pair ofright and left lens chamber units, each unit including a test window andoptical elements to be selectively disposed in the test window; and acontroller including a transmitting part which transmits a controlsignal in the form of an optical signal to the lens chamber units toselectively dispose the optical elements in the test window, thetransmitting part being adapted to widen an extent of diffusion ofluminous flux of the optical signal more greatly in a forward to upwarddirections than in a lateral direction.
 2. The optometric apparatusaccording to claim 1, wherein the transmitting part includes a lightemission part which emits the luminous flux of the optical signal and anoptical element which is mounted directly ahead of the light emissionpart and deflects a part of the luminous flux emitted from the lightemission part upward.
 3. The optometric apparatus according to claim 2,wherein the optical element has a reflection face at which the part ofthe luminous flux emitted from the light emission part is deflectedupward.
 4. The optometric apparatus according to claim 3, wherein anslant angle of the reflection face is determined so that an incidentangle of the luminous flux emitted from the light emission part onto thereflection face is larger than a critical angle.
 5. The optometricapparatus according to claim 3, wherein an slant angle of the reflectionface is determined at 45° or less with respect to a center axis of theoptical element.
 6. The optometric apparatus according to claim 2,wherein the optical member is rotatably mounted directly ahead of thelight emission part.
 7. The optometric apparatus according to claim 1,wherein each of the lens chamber units includes a lens disk holding theoptical elements and a motor which rotates the lens disk, and thetransmitting part transmits the control signal for driving the motor.